Ken Barlow (Bill Roache) lies at the bottom of the stairs ... but who was at the top?
Photograph: ITV PLC

Who pushed Weatherfield veteran Ken Barlow down the stairs, leaving him for dead? The shoving of Coronation Street’s longest-serving character on Monday night marked the moment the carousel of British soap-opera gimmicks clacked around once more to one of the genre’s mainstays: the whodunnit.

It’s a trope that dates back to 1980, when internationally popular US saga Dallas ended its third season with the shooting of JR Ewing, leaving viewers to wait months for the new series to reveal the culprit. Soaps have been recycling the formula ever since, with EastEnders’ “Who shot Phil Mitchell?” storyline of 2001 and Neighbours’ 2010 “Who pushed PR?” arc among the most blatant homages.

That feverish summer of 1980 demonstrated the magic of a good soap mystery: the show starts to publicise itself. Thirty-seven years ago, there were “I Shot JR” badges, quips during the Carter v Reagan presidential race and rumours that the Queen Mother had been to the bookies to bet on the shooter being JR’s wife, Sue Ellen. These days, blogs, vlogs and social media – all offering easy PR for programme-makers – fulfil the same purpose. The list of suspects helpfully released by ITV to accompany Monday’s broadcast – plus clues that will be dripfed via Instagram, Twitter and Facebook – showed how far the trick has evolved, although all the intel could be part of the game. Indeed, in 2015, EastEnders ended a year of “Who killed Lucy Beale?” marketing by naming 11-year-old Bobby Beale, who had never been on any official lists and hadn’t been suspected by fans.

As well-worn as they may be, whodunnits often help with soaps’ struggle to retain casual viewers. The bludgeoning of Archie Mitchell in EastEnders on 25 December 2009 required Christmas newcomers to stick around throughout January before another perennial attention-grabber, a live episode, revealed the villain. Emmerdale’s most memorable mystery, the defenestration of Tom King, also happened during a festive special – and wasn’t solved for five months. But the battle for supremacy between the big soaps is a year-round event, making spring as good a time as any to steal a march.

As for Corrie, Monday night’s episode sent Ken sprawling before the ad break, leaving time to cycle through several suspects, all of them looking perhaps more guilt-ridden than in any previous soap riddle. It’s unsophisticated storytelling but it’s in vogue right now on TV; classily executed as they are, the likes of Unforgotten and Broadchurch use the same audience-manipulating mechanism. If Corrie can borrow a bit of their style, Barlow’s broken bones might make for great telly. And, even if it doesn’t, a short-term ratings boost for those famous cobbles is all but guaranteed.